The invention relates to a method for applying a structure made from a structural material onto a semiconductor element and also to a semiconductor structure.
Methods are known in semiconductor technology to deposit thin metallization structures onto a semiconductor element. Thus it is known, for example, to deposit a metal structure onto a silicon wafer, wherein a photosensitive lacquer is initially deposited onto the silicon wafer. The photosensitive lacquer is then exposed via an exposure mask, so that the areas of the photosensitive lacquer on the silicon wafer at which, at a later time, metal should be located on the surface are exposed. After the exposure, the lacquer is developed so that the exposed areas of lacquer are removed.
In the next step, a metal film is now deposited over the entire surface, so that, first, the metal film lies on the remaining lacquer and, second, the metal film is deposited on the silicon wafer in the areas in which the lacquer was removed.
Finally, through the use of solvents, the remaining lacquer is also removed, so that, in this step, the metal film is also removed in the areas in which it lies on the lacquer.
As a result, a predetermined metal structure remains on the silicon wafer. The method described above is also known as the “lift-off method.”
In this method, it is essential that the solvent must reach through the metal film to the lacquer lying under the metal film, in order to strip this lacquer. For this purpose, either long processing times for the stripping process are needed, so that the solvent can penetrate via small pores through the metal film or alternatively the lacquer can be stripped in some areas, so that the stripping process eventually continues to all of the areas covered with lacquer.
Likewise, from U.S. Pat. No. 3,934,057 it is known to perform a two-stage lacquer coating method, so that, after the deposition, the metal film does not form a connection over an area, but instead, the areas in which the metal film lies on the lacquer and the areas in which the metal film lies directly on the silicon wafer are separated from each other by gaps. In this way, the solvent can reach through the mentioned gaps to the lacquer.
This method, however, has the disadvantage that a cost-intensive and time-intensive lacquer coating step with at least two stages is required.